1. Field of the Invention
The present invention relates to a recording apparatus which adds information other than image information to be printed on a printing medium. More particularly, the present invention relates to a device and method which enable additional information corresponding to image information to be remote-readably recorded in a state of being combined with the image information when the image information is printed on a printing medium output from an image forming apparatus such as a printer, a copying machine, or a plate-making apparatus having a printing mechanism for recording information on a printing medium such as paper using toner or ink.
2. Description of the Related Art
Known techniques for preventing a leak of information from confidential documents include, for example, a method of using a printing medium on which a latent image is formed in advance (see, for example, Japanese Patent Laid-Open Publication Nos. Hei 9-295484, 6-212123, 6-239078, and 7-76196) and a method of using an electronic latent image, i.e., a method in which a latent image is formed together with image information when a confidential document is formed, and the latent image becomes visible on a printing medium as well as the document when the confidential document is copied (see, for example, Japanese Patent Laid-Open Publication No. 2001-197297). If such a latent image is used in a confidential document, an unauthorized copy made from the confidential document can be easily discriminated.
The method of using a latent image, however, is effective only when a copy is made can be visually inspected. If an unauthorized copy is put in a bag or the like or inserted between other documents such that the copy cannot be seen, the copy of the confidential document can be removed. Thus, the method of using a latent image has a problem in terms of maintenance of secrecy.
A technique for remotely sensing commodity products by attaching a magnetic material to commodity products and using magnetostrictive vibration or the large Barkhausen effect is known (see, for example, National Publication of International Patent Application No. Hei 7-503061 and Japanese Patent Laid-Open Publication No. Hei 8-185496). This technique is utilized in stores where compact discs or the like are sold. That is, unless certain processing is performed on an article to prevent emission of a magnetic field from the article when the article is brought out of a store, a magnetic field emitted from the article is remotely sensed by a magnetic material sensor placed at an exit of the store to issue a warning. Unauthorized removal of the article is thereby prevented. If this technique is used, a confidential document can be remotely sensed by a magnetic material sensor even when it is put in a bag. However, if a copy of the confidential document is made, unauthorized removal cannot be detected since no magnetic material is added to the copy.
The existence of a confidential document to which a magnetic material is added can be remotely detected, as described above. The above-described sensing technique is therefore considered effective in preventing information leakage. However, no means has been provided to enable on-demand addition of a magnetic material to a copy.